The present invention relates to integrated circuits, and more particularly, to a method of making a solder pad for an integrated circuit.
Solder pads provide both electrical and mechanical connections, as well as a thermal path, between electronic components. Typically, solder balls or bumps are deposited onto the solder pads and reflowed to form respective solder joints between the electronic components. A conventional method of making a solder pad 10 will now be described with reference to FIGS. 1 through 4. Referring now to FIG. 1, a substrate 12 having a metal layer 14 formed thereon is shown. A photo resist 16 is applied to the metal layer 14 and exposed through a photo mask 18 placed over the photo resist 16. Referring now to FIG. 2, the photo mask 18 is removed after exposure and the photo resist 16 is developed, exposing portions 20 of the metal layer 14. Referring now to FIG. 3, the metal layer 14 is selectively etched through the developed photo resist 16 to form the solder pad 10. As shown in FIG. 3, portions 22 of the substrate 12 are exposed by the etching operation. Referring now to FIG. 4, a solder mask 24 is formed on the exposed portions 22 of the substrate 12 and a portion 26 of the solder pad 10. A solder ball or bump 28 is deposited on the solder pad 10. Because the reliability of the solder joints formed between the electronic components is dependent on the adhesion of the solder ball 28 to the solder pad 10, there is a need for strong adhesion between the solder pad 10 and the solder ball 28 deposited thereon.
It would be desirable to have a method of making a solder pad that enhances adhesion of the solder ball to the solder pad.